Known speed measuring devices of the aforementioned type include an encoder wheel in the form of an annular disk or cylindrical shield of magnetized rubber which is angularly constrained to the rotating ring of the bearing. In some known solutions, the encoder wheel comprises a metallic insert which is fixed by means of gluing to the magnetized rubber portion and is force-fitted onto the rotating ring of the bearing or onto an element integral therewith. In other solutions, instead, the encoder wheel is directly mounted onto the rotating ring and is angularly constrained to the rotating ring by means of gluing.
It has been found, however, that in the case where they are glued onto the metallic insert, the encoder wheels are subject to tension which they do not withstand well, whereas in the case where they are glued directly onto the rotating ring, the encoder wheels are difficult to position.